Temperature control in shock-chilling petroleum vapor phase conversion products



w. w. HOLLAND 2,608,527 TEMPERATURE CONTROL IN SHOCK-CHILLING PETROLEUMVAPOR PHASE CONVERSION PRODUCTS Filed Aug.. l, 1947 Aug. 2G, 1952 .N .mi

Patented Aug. 26, 1952 TEMPERATURE CONTROL IN SHOCK-CHILL- ING PETROLEUMVAPOR PHASE CONVER- SION PRODUCTS William Holland, Baltimore, Md.,assignor to The Gyro Process Company, Detroit, Mich., a

corporation of Michigan Application August 1, 1947, Serial No. 765,438

(Cl. 19E-61) 12 Claims.

This invention is directed to the cracking of hydrocarbons in the vaporphase, and particularly to the therrnolytic conversion of relativelyheavy `liquid hydrocarbons into products boiling temperatures involvedthat the reaction will proi ceed too far or secondary reactions occurunless Aadequate precautions are taken to check the progress of thereaction suddenly and at precisely the correct point. There is also theever-present danger of excessive coke formation unless the reactionconditions are under definite and positive control.

The practice of shock-chilling the products of conversion reactions hasbeen followed in some vapor phase cracking` processes by directlycontacting the hot vapors emerging from the conversion zone with arelatively cool oil in a quenching zone, thus reducing the temperatureto a point where the cracking reaction ceases, but the results have beenonly measurably satisfactory because of the absence of any deiinitemeans ci exact temperature control at this critical stage of theconversion operation. If the temperature is not substantiallyinstantaneously reduced to the proper degree at this stage, andmaintained relatively constant, not only will the cracking reactioncontinue beyond the desired point but coke will be formed in thequenching Zone, causing a premature shut-down of the equipment and thelo'ss of valuable operating time. Also if the temperature is reducedonly to a point below that required for cracking or below the criticalcoking temperature, the chilled products have a marked tendency todeposit granular carbon in the transfer lines between the quenching Zoneand the `after equipment, eventually plugging the lines andnecessitating major repairs. On the other hand, if the temperature isreduced to too W a degree, undesirable condensation results and the Itis, therefore, an object of this invention to provide efficient andreliable means of controlling the temperature of the vapor phasecracking operation at the critical stage between the period of maximumcracking and that at which cracking has ceased-altogether, and to reducethe time element at this stage to the shortest possible interval.

It is also an object of this invention to provide means whereby thedeposition of coke in the transfer lines between the quenching zone andthe fractionating column is reduced to; a minimum, and such granularcoke as may be held in suspension in the oil is collectedin a-connedVarea and removed from the system without interfering with thecontinuous operation ofthe process'- Y It isa further object of thisinvention to `retain sufficient residual heat in the products -of thequenching operation to cause the fractionating column to functionproperly andefciently in effecting the desired separation of the lightand heavy fractions resulting from the pyrolytic conversion operation. ii l w Other objects ofthis invention will'become apparent as furtherdetails ofthe process are set forth. Y l `inthe vapor phase conversionof .liquid hydrocarbons for the production of high grademotor fuel,temperatures in excess of 1100 Rare-usually required, and forparticularly refractory charging stocks, suchas cycle stocksproduced inprevious cracking operations, temperaturesof the order oi 1250 to 1350F. are-not infrequently required. In the case of gaseous chargingstocks, however, such as, for example, the saturated C2, C3 and C4compounds generally used in the pyrolysis of gases for the production ofunsaturated hydrocarbons for chemical synthesis, the conversiontemperatures may range from 1350 to 1550" F. But "inl, `either case,whetherthe charge is normally in the liquid or gaseous state, thetemperature of the products of the conversion reaction must be reducedas nearly instantaneously as possible, immediately upon emergence fromthe cracking zone, to a degree where cracking ceases altogether. Severalfactors may govern the optimum temperature at this point, themostimportant of which is that it must be below lthe temperature atwhich further pyrolytic decomposition can take place or coke can beformed, and it must be below the temperature at which secondaryreactions occur. On the other hand, the vapors preferably must retainsufiicient residual heat for the required fractionating purposes, whichis governed by the degree of separation desired, which in turn isdependent upon the height of and the number and emciency of the bubbletrays in the fractionating column. Generally speaking, quenchingtemperatures not substantially in excess of 600 F. are suitable for thepurpose; but Ythe exact temperature best suited to an individualoperation should be calculated from theoretical considerations orpreferably determined by experimental methods.

The choice of a cooling medium for use in quenching operations or forshockech'illing the cracked vapors issuing from the conversion zone is amatter of convenience rather than exact specifications. Any relativelylight distillate that is clean and free from sediment and that Will notbe completely vaporized when brought into contact with the hot vaporswill serve the purpose. However, it should contain no heavy fractionssubject to cooking under the temrerature conditions prevailing in thequenching zone. It is preferable, of course, to select a distillatefraction produced within the operation itself, rather' than from anextraneous source. For this` purpose, thereforer a suitable stream ofoil may be withdrawnfrom a tray at an intermediate point in thefractionating column. This material, after cooling, is collected in aworking tank 'from which it is delivered to the top of the temfperaturearrester or quenching chamber where by suitable mechanical means, suchas atomizing spray nozzles, it is intimately mixed in direct contactwith the hot vapors issuing from the conversion zone.

vThe novelty of this invention resides primarily in the design of thequenching chamber and means of controlling the temperature therein,together with its relation to the fractionating column, with respect tothe disposition of coke lduringA the passage of the products ofconversion from one tothe other.

Since the temperature maintainedv in the quenching chamber is dependentupon the quantity of oil delivered thereto from the working `tank, itlis obviously vdesirable vthat the' Vrate of 'oil now should be governedby the temperature.

It r should be stated in this connection that the ilsmoothne'ss of theentire conversion operation, "as well as the uniformity in quality' ofthe nal 'products'. isY more largely dependent upon acculratetemperature control throughout the system than any other single factor.Heretofore "little importance has been attached to the maintenance ofVan exact degree of temperature in the 'quenching zone, a feature whichhas contributed :to the varying character of the nal products andvinconsistent yields, as well as promoting the formation of coke underfluctuating temperature conditions. It is therefore a primary object of'this invention to provide positive means of controlling the temperatureat this point and completely checking the rapid pyrolyticdecomposivvtion of thev hydrocarbon charge at the proper ners, extensiveexperimental work and the care- .ful study of 'heating problems bydesigning en- Igineers, but the samel attention, soA far as I am `aware,has never been directed tothe simpler -yetl equally important problem ofdealing with the decomposition products of hydrocarbons as they leavetheconversion zone.

Vany requirements.

It is neither practical nor economical to maintain the quenching oil inthe Working tank at a constant temperature because of its relativelylarge volume and the varying atmospheric and cooling water temperatures,yet any substantial variation` in the temperature of the oil deliveredto the quenching chamber is reflected immediately in the character ofthe cracked products leaving the chamber, as is clearly shown byfr-equent analyses of the end products. On the other hand, it has beenobserved that if the quenching chamber is maintained at a reasonablyconstant temperature, the character of the conversion products isuniform and the yields consistent, and little or no coke is formed inthe quenching operation.

To thisend a temperature control system is provided, the mechanism ofwhich consists essentially of a thermostatic element inserted throughthe wall of the quenching chamber, electrically connected with a sourceof current and means for automatically controlling the delivery of astream of cool oil from the working tank to the quenching chamber as thethermostatic circuit is established or broken. This arrangement aifordsample means of maintaining a constant temperature in the quenchingchamber or of regulating the temperature in accordance with If Y thetemperatur-e in the chamber rises, a larger quantity of cooling oil isadmitted thereto; if the temperature falls, the supply of oil isdiminished.

The quenched products of conversion, now reduced in temperature to about600 F., usually include a small amount of iinely divided carbon or sootwhich should be removed from the system before the other products enterthe iractionating tower. This is accomplished by means of a flash drum,acting as a trapY for the solid materials which settle to the bottombecause of their higher specific gravity and greatly reduced velocity atthis point of the operation; while the liquid, vapors and gases areflashed off with the aid of steam under partial pressure conditions,leaving the top of the flash tower and passingA directly to thefractionating column. The solid materials, along with arsmall amount ofVtar formed in the cracking operation, are withdrawn from the bottom ofthe flash. tower and diverted from the system.A

In vapor phase cracking operations, there is always the possibility ofthe deposition of finely divided coke in horizontal transfer linesV ofany considerable length between the quenching chamber and thefractionating column. This invention is particularly directed to theavoidance of such a condition. To thisend, the quenching chamber isprovided with a conical bottom constructed on about a sixty degreeangle'to facilitate the complete and rapid exit of the quenched productsfrom the bottom of the chamber, the turbulence within washing the wallsof the cone free of carbon. Immediately below the cone is a pipe ttersspool about twelve inches in length in which a helical vane is placed.Because of` the high velocity of the materials passing through the spooLthis vane imparts a-rapid spiral or swirling motion to the liquid andvapors which eiectively scrub the inner walls; of the comparativelyshort line leading to the ash drum, thus avoiding the deposition of cokebefore it is trapped at the desired point in the bottom of the ash drum,from which it is withdrawn in the form of a suspension in the liquidresidue. The placing of bailies in the flash drum vane; and

.tobstruct theyupward passage of the finely idivided -co'ke particles isoptional, although experience indicates that the increased velocityresultig therefrom renders the advantage of bailles questionable.` i i vThis invention will be clearly understood by `'referenceto `theaccompanying simplied flow diagram forming a part of these specications,in which Fig. l represents in partial section and 'side elevationapparatus and equipment adapted tothe `continuous performance of thefunctions `and operationsV herein described;

f' l Vlig. `is anenlarged longitudinal section of the pipe viittersspool containing the helical Fig. 3 is a transverse cross section of thespool .Referring t0 the drawing, the numeral l repre- A-sents a tankcontaining a liquid hydrocarbon charging stock such as crude oil, toppedcrude,

gas oil, kerosene or the like, which is delivered by pump 2 through line3 to an intermediate point .in the fractionating column iwhere it frstserves as a reflux for, and is preheated by,

the hot ascending cracked products of the conversion operation.A Thepreheating `ci? the charge or,V feed stock,` however, vis not limited tothis means alone, since itis customary to `take ladvantage' of anyeconomical source of heat exchange wherever possible in such systems,especially when charging crude oil, in which event the natural gasolineis usually removed through heat exchange with hot products, such asresiduum from the evaporator, before entering the cracking coils in thefurnace.

The` preheated feedstock, mixed with condensate produced within the.fractionating column, is withdrawn from .the `bottom of the columnthrough `line 5, controlled by valve 6, and is de- `liveredby pump 'l toa vaporization coil 8 `lo- `catedpreferably in the convection section ofa furnace 9 where it is substantially converted into vapor.` Thevaporized and unvaporiaed portions of the charge or feed then passvthrough line Hi into an evaporator lIl where Vaporization is effectedwith the aid of steam under partial pressure conditions, the unvaporizedheavy residue being withdrawn fromthe bottom of the evaporator throughline l2, controlled by valve i3, and divertedvfromthe system.` Thisresidue may be 'subjected to a-viscosity-breaking operation, run

to coke or processed by any suitableY means for the production of roadoil, bunker C iuel or other desirable products.v

The oil vapors leaving the top of the evaporator, commingled :withsteam, pass through line i4 and enter the cracking coil i5 Where thecon- `lversion` into i lighter products is effected.

V.Any suitable arrangement of preheatingcoils, drying coils or crackingelements may befused for .this purpose, depending upon the character` ofthe charging stock and the endproducts desired, That is to say, whetherthe charge is normally in the liquid or gaseous state, or `whether the`final ,products are to beused primarilyiforthe purpose of `motor fuelor `asunsaturated hydrocar-` bons for the synthesis of chemicalcompounds, or for both purposes. w

The process herein described is adapted to the conversion of eitherliquid Aor gaseous `hydrocarbons, although in the latter case, asomewhat different `arrangement ofA equipment is required and higherconversion temperatures are employed. For` example, when chargingl aliquid Ahydrocarbon according to Fig. 1 of the accompanying drawing,conversion temperatures of the rl 6 order of 1000 to 1350" F. maybeadequate `for the'desired conversion; While if the :chargeisin the`gaseous state underrnormal' temperature and pressure conditions,theconversion temperatures 'quenching chamber I1 where by direct andintimate contact with relatively cool atomized oil,

the temperature of the highly heated vapors is substantiallyinstantaneously reduced to adegree below that at which furtherdecomposition.

`can take place, secondary reactions occur `or coke be formed. Yet thevapors must retain sufficient residual heat to cause the fractionatingcolumn to function iproperly.- These requisite conditions can be metonly by accurate temperature `controlof the quenching chamber, uponwhich the ultimate yields and quality of the finished products largelydepend. Y

The fractionating column, which is preferably of the bubble towerdesign, provides a suitable source of oil for the quenching opera-tion,a selccted stream being withdrawn from an .inteme- `diate `bubble trayfor thisA purpose, Vleaving the tower through line i8 and passingthrough a water cooler I 8 into-the Working tank `20,'from which itisdeliveredby pump 2| through line 22, controlled by valve 23, into thetop of the quenching chamber I1 where it is atomized by nozzles 24,contacting the heated vapors at this pointas previously stated. i A

Somewhat less cooling oil is supplied thrQllgh valve 23 than the totalamount required for the i complete quen-ching operation, theremaindenbeling routed through a by-pass 25, around valve 23.

It is this portion of the cooling oil that is used for regulating thetemperature in the quenching chamber, Yits rate of flow being governedauto- `matically by thermostatic control of a ,quick-1opening-and,-closing valve 26, or any other means `design-ed for theaccomplishment of the same purpose. The by-pass provides more `delicateand accuratetemperature adjustment than if the entire volume of coolingoil were placedV under thermostatic control. It also insures asuiiicient quantity of oil reaching the quenching chamber at all times,since the major portion of the oil iiowin-g continuously through `valve23 may be manuallycontrolled in the event of failure of the automaticsystem through mechanical defects or otherwise. i f

Various mechanical devices involving theuse Vof motors, pumps, valvesand the like are availfing oil, in addition to that passing continuouslythrough valve 23, for the complete quenching` of able for automatictemperature control `under thermostatic conditions, any of which may beus-ed for the purpose at hand; but for reasons of simplicity andreliability, with no intention of limiting the scopeof this invention, Iprefer the quick-opening-and-closng valve in the bypass 25 to supply theregulatory quantity of coolthe hotvapor issuing from the cracking coili5. Valve 26 may be magnetically actuated to the open or closed positionas the` thermostatic cirfecit. Ais' established or broken by the rise orfall of the `temperature in the quenching chamber.

vThe thermostatic element 21 inserted through the Wall of the chamber iselectrically connected with the, magnets 29 through conduit 28 and witha source of current (not shown) in such .a manner as to control themovem-en-t of the valve mechanism 30 to the open or closed position inresponse to the uctuationof temperature in the chamber. When thetemperature rises above the desired point, valve 26 is openedautomatically, admitting more oil to the chamber; when the temperaturefalls, the valve is closed, diminishing the iiow of oil, thusmaintaining an even temperature in the quenching chamber.

The bottom of the quenching chamber is constructed in the form of a cone30, the walls oi which are built on an angle of approximately sixtydegrees to facilitate the ready eXit of the materials from Ithe bottomof the chamber, espeoially `any coke particles held in suspension in theoil. Immediately below the cone, and hanged thereto, is a pipe iittersspool 3|, in which is placed a helical vane 32, more clearly shown inthe enlarged sectional drawings, Figs. 2 and 3, which imparts a rapidspiral or swirling motion tothe oil and vapors as they enter thecomparatively short pipe 33 leading to the flash tower 34, scrubbing theinner walls of the pipe free of carbon in transit.

Reaching the hash tower at reduced pressure, the vaporous fractions aredashed oi, preferably with the aidv of steam injected into the lowersec- `tionV ofthe tower,l while the residue holding the carbon insuspension is diverted from the system through line 3'5, controlled byvalve 3G. The

-flashed Vvapors leaving the top of the tower throughline 31 enter thefractionating column 4 where separation of theV light and heavyfractions is eiected, also, if desired, with the aid of steam injectedinto the bottom of the column. The overhead vapors and gases leaving thefractionvating column through line 38 are conducted through a condenser39 and collected in a receiver or separator 40, from the bottom of whichAthe cracked distillate is withdrawn through line 4|-, controlled byValve 42, .and sent to the treating system; while the uncondensed gasesleaving the top of the receiver through line 43, controlled by valve 44,go to the gas recovery system.

VThe temperature of the top tray in the frac- Ai'sionating column, whichgoverns the end point of the distillate produced, is controlled by thequantity of distillate returned to the top of the column y' through line45Y by means of pump 46.

I claim:

I. In a vapor phase cracking apparatus for the conversion ofhydrocarbons, a conversion arrester comprising a quenching chamber,means in the upper part of said chamber forfintroducing therein aquenching agent in a lnely divided form, means for introducing convertedhydrocarbonsintosaid chamber for contact with said quenching agent, thechamber being formed with a conical bottom, a ilash tower, a transferline leading from the conical bottom of said quenching chamber to thelower part of said flash tower,

'helical means disposed in said transfer line to impart a rapid swirlingmotion to the materials passing therethrough, a vapor line leading fromthe top of said flash tower, and means for diverting from the systemliquid residues and -suspended' carbon trapped in the bottom of the iashtower.

2. In a vapor phase cracking apparatus for hydrocarbon products, -aconverter for converting hydrocarbons therein,` a conversion arrestercomprising a hollow body dening an internal quenching chamber, means fortransferring converted hydrocarbons from said converter to said chamber,means in said chamber for contacting the convertedy products introducedtherein with a quenching agent in a nely divided form, a flash tower, atransfer line leading from the bottom o1' the quenching chamber of saidarrester to said tower, means in said transfer line `for imparting arapid swirling motion to the materials passing therethrough, Vaporoutlet means leading from the top of said flash tower, and means forwithdrawing from the bottom of said tower liquids and solids presenttherein.

3. In a vapor phase cracking apparatus. for the conversion ofhydrocarbons as deiined in claim 2, wherein the` bottom of the flashtower is provided with means4 for introducing steam therein.

Ll. A conversion arrester for use in vapor phase cracking systems forthe molecular conversion of hydrocarbons, said arrester comprising areceptacle formed with an internal quenching chamber, means forintroducing converted hydrocarbons into the upper part of said chamber,spray means arranged in the upper part of said chamber for bringing aquenching agent in a nely divided form into direct and intimate contactwith the converted hydrocarbons to reduce the temperature of the lattersufficiently to substantially arrest conversion reactions, saidquenching chamber being formed with a substantially conical bottomterminating in a flanged outlet, a flanged spool secured to said fdangedoutlet to form a continuation thereof, and a helical vane means disposedin said spool and operative to impart a` rapid swirling motion tomaterials passing therethrough from said quenching chamber.

5. In a vapor phase cracking system for the conversion of hydrocarbons,means for heating hydrocarbons, a conversion arrester having an internalquenching chamber into which the converted hydrocarbons are introduced,spray devices in said chamber, means for forcing a relatively coolhydrocarbon distillate through said spray devices to bring thedistillate in a finely divided form into direct and intimate contactwith said hydrocarbon vapors, means constituting a iiash chamber,transfer conduit means of reduced cross-sectional area in relation tothat of said chambers for transferring hydrocarbons from the bottom ofsaid quenching chamber to said flash chamber, helical vane. meansarranged in said conduit means for imparting a rapid swirling motion tothe hydrocarbons passing therethrough, vapor outlet means leading fromthe upper part of said ash chamber, and means diverting from the systemresidual hydrocarbons contained in the bottom of the flash tower.

6. In apparatus for the molecular conversion of hydrocarbons in thevapor or gaseous phase, a'converter through which vaporous hydrocarbonsare passed and heated to reaction temperatures, drum structuresproviding separated quenching, flashing and fractionation chambers.means for passing the heated products of said converter to saidquenching chamber, means for introducing into the top ofV said chamber aliquid hydrocarbon distillate in a finely divided form for direct andintimate contact with said converted products to effect a substantiallyinstantaneous reduction in temperature of the converted products tonon-reacting temperatures, means for transferring the quenched productsfrom the bottom of said quenching chamber to the lower part of saidflash chamber, vapor outlet means leading from the top o said flashchamber to the lower part of said fractionating chamber, liquid outletIneans for the withdrawal of a heavy residual from the bottom of saidiash chamber, fractionating trays provided in said fractionating chamberin vertically superposed order, vapor outlet means in the top of saidfractionating column, vapor liquid outlet means leading from the top ofsaid fractionating chamber above said trays, liquid outlet means leading1from said fractionating chamber intermediately of the height thereoffor advancing the same as the cooling distillate into the top of saidquenching chamber, thermostat means associated with said quenchingchamber, and means governed automatically by said thermostat means andthe operating temperatures' within said quenching chamber for increasingor diminishing the flow of the cooling distillate to said quenchingchamber, whereby to maintain a constant temperature in the quenchingchamber.

7. In apparatus for the molecular conversion of hydrocarbons in thevapor or gaseous phase as specified in claim 6 in combination with meansfor introducing steam under regulated now into the bottoms of said flashand fractionating chambers.

8. In a vapor phase system for the molecular conversion of hydrocarbons,a conversion arrester dening an enclosed quenching chamber, means forintroducing converted hydrocarbons into said chamber, spraymeans in saidchamber for bringing a relatively cool hydrocarbon distillate in aiinely divided form into intimate and direct Contact with the convertedhydrocarbons, vapor fractionating means, a transfer conduit leading fromthe bottom of said quenching chamber to said iractionating means, meansfor withdrawing at an intermediate point from said fractionating means aquenching distillate, pipe means for advancing said quenchingdistillate` to the spray means in said quenching chamber, anelectro-responsive valve in said pipe means for increasing anddecreasing the rate of ow of the distillate through said pipe means, anoperating circuit for said valve, and a switch in said circuitresponsive to the internal temperatures of said quenching chamber toopen and close said valve, n

9. In a process of converting hydrocarbons in the vapor phase, the stepsof converting hydro-` carbons at temperatures between 1000 F'. and 1550F., introducing the converted hydrocarbons into a conversion arrester,spraying the converted hydrocarbons with a cool hydrocarbon distillatein said arrester to Substantially instantaneously reduce the temperatureof said hydrocarbons to reaction-arresting temperatures of the order of600 F., and maintaining the arrester at a constant temperature, byregulating the rate of flow of hydrocarbon distillate thereto inresponse to valve means thermostatically controlled by the temperaturein said arrester.

10. In a process of converting hydrocarbons in the vapor phase, thesteps of converting hydrocarbone at temperatures between 1000 F. and1550o F., introducing the converted hydrocarbons into a conversionarrester, spraying the converted hydrocarbons with a cool hydrocarbonquenching medium in said arrester to substantially instan taneouslyreduce the temperature of said hydrocarbons to reaction-arrestingtemperatures of the order of 690 F., and continuously controlling thequantity of quenching medium to be sprayed and maintaining thetemperature in the arrester constant by bypassing a quantity of the saidquenching medium in response to thermos-tatie control by the temperaturein the arrester.

11. In a process of converting hydrocarbons in the vapor phase, thesteps of arresting the conversion reactions with a quenching medium in aquenching zone maintained at a constant temperature, transferring thearrested reaction products to a flashing zone, and imparting a rapidlyswirling motion to the arrested reaction products during such transfer.

12. In a vapor phase cracking system forthe conversion of hydrocarbons,the combination including a quenching chamber, said chamber beingprovided with a conical bottom, a spool flanged to the lower end of saidconical bottom, a helical vane disposed in said spool, a tower, aconduit connecting said spool to said tower, a thermostat associatedwith said quenching chamber, a conduit entering said quenching chamberfor providing a fluid quenching medium thereto, valve means associatedwith said last named conduit for controlling the flow of fluid quenchingmedium to said chamber, and means controlled by said thermostat operableto increase or decrease the ow of iiuid quenching medium through saidvalve means to the quenching chamber, whereby the temperature in saidchamber is maintained constant by automatic control.

WILLIAM W. HOLLAND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,683,826 Huff Sept. 11, 19281,850,429 Wagner Mar.. 22, 1932 1,910,242 Chitticl: May 23, 19331,927,829 Harnsberger et al. Sept. 26, 1933 2,154,795 Westenberg Apr.18, 1939 2,171,522 Finsterbusch Sept. 5, 1939 2,346,642 Babcock et al.Apr. 18, 1944 2,389,399 Alther Nov. 20, 1945 2,431,485 Keeling Nov. 25,1947

10. IN PROCESS OF CONVERTING HYDROCARBONS IN THE VAPOR PHASE, THE STEPSOF CONVERTING HYDROCARBONS AT TEMPERATURE BETWEEN 1000* F. AND 1550* F.,INTRODUCING THE CONVERTED HYDROCARBONS INTO A CONVERSION ARRESTER,SPRAYING THE CONVERTED HYDROCARBONS WITH A COOL HYDROCARBON QUENCHINGMEDIUM IN SAID ARRESTER TO SUBSTANTIALLY INSTANTANEOUSLY REDUCE THETEMPERATURE OF SAID HYDROCARBONS TO REACTION-ARRESTING TEMPERATURES OFTHE ORDER OF 600* F., AND CONTINUOUSLY CONTROLLING THE QUANTITY OFQUENCHING MEDIUM TO BE SPRAYED AND MAINTAINING THE TEMPERATURE IN THEARRESTER CONSTANT BY BYPASSING A QUANTITY OF THE SAID QUENCHING MEDIUMIN RESPONSE TO THERMOSTATIC CONTROL BY THE TEMPERATURE IN THE ARRESTER.